Today, for milk, juice and other beverages, there exists a number of types and sizes of consumer packages, e.g. Parallel epidemic packages of laminated paper/plastic, blow moulded bottles or cups made solely of plastic and different kinds of containers made of glass, sheet metal or aluminium. A number of these different kinds of packages comprise some kind of opening device in order to facilitate the access of the consumer to the contents of the package either for pouring into a drinking-vessel or for consumption directly from the package. In case of packages formed as bottles, a common solution is some kind of screw cap, while packages formed from plastic or laminated paper/plastic often comprise a simple tear notch or a pre-made pouring opening covered by a strip adapted to be torn off, a so-called pull-tab. Separately made opening devices of thermoplastic material, e.g. injection moulded opening devices with a pouring edge or a short neck and a snap or screw cap are also known. This kind of opening devices can also be injection moulded in situ, i.e. around an opening punched from the packaging material such that this opening is closed until the consumer opens the opening device. Injection moulded opening devices can of course also be of different size and even cover a complete upper surface of a packaging container, whereby they also serve as a side panel of the packaging container.
Especially in case of the above mentioned injection moulded opening devices is it common to seal the pouring opening with some kind of membrane that can be torn off, which membrane on one hand guarantees that the opening device is completely tight before it is opened, and on the other hand indicates that the package has not been opened before (tamper proof). The membrane is often also utilised in case of the kind of opening devices that have a screw or snap cap for the reclosure. In order to make the removal of the membrane possible, the membrane is of the provided with some kind of grip or pull device, which makes is possible for the consumer to get a firm grip in order to especially promote the initiation of the opening. Even in cases where the membrane is demarcated from the surrounding opening device or surrounding portions of the package, the initiation of the tearing can in some cases cause difficulties, since the weakening line in spite of its obvious weakening purpose is not allowed to weaken the material in such an extent that ruptures and leakage occurs, Earlier attempts to eliminate this difficulty at the initiation of the tearing has in substance been directed towards minimising the necessary force by making sure that the weakening line has a minimal remaining material thickness, but since the manufacturing tolerances are comparatively large a relatively large material thickness must be present in order to secure that leakages do not occur. Other possibilities to facilitate the initiation of the tearing is of course to provide the grip device with a sturdy pull ring or equivalent grip that makes it possible for the consumer to apply a large pulling force on the membrane at the initiation of the tearing.
Thus, it is a common desire to provide an opening device of the above-mentioned kind, by which the initiation of the tearing of the membrane is facilitated without the occurrence of any of the above-mentioned drawbacks.